Carbon nanotube composite film and method for making the same

ABSTRACT

A carbon nanotube composite film includes a treated patterned carbon nanotube film and a polymer film having the treated patterned carbon nanotube film located therein. The treated patterned carbon nanotube film includes carbon nanotube linear units spaced from each other and carbon nanotube groups spaced from each other and combined with the carbon nanotube linear units. A method for making the carbon nanotube composite film is also disclosed.

RELATED APPLICATIONS

This application claims all benefits accruing under 35 U.S.C. §119 fromChina Patent Application No. 201210333727.2, filed on Sep. 11, 2012 inthe China Intellectual Property Office, the disclosure of which isincorporated herein by reference. This application is related tocommonly-assigned applications entitled, “METHOD FOR MAKING CARBONNANOTUBE COMPOSITE FILM,” filed **** (Atty. Docket No. US46256); “CARBONNANOTUBE COMPOSITE FILM,” filed **** (Atty. Docket No. US46254).

BACKGROUND

1. Technical Field

The present disclosure relates to a carbon nanotube composite film andmethod for making the same.

2. Discussion of Related Art

A transparent conductive film has characteristics of high electricalconductivity, low electrical resistance, and good light penetrability.The transparent conductive film is widely used in liquid crystaldisplay, touch panel, electrochromic devices, and airplane windows.

The conventional methods for forming the transparent conductive filminclude a vacuum evaporation method and a magnetron sputtering method.The drawbacks of these methods include complicated equipment, high costand being unsuitable for mass production. Furthermore, these methodsrequire a high-temperature annealing process which will damage asubstrate on which the transparent conductive film is formed. Thesubstrate with a low melting point cannot be used for forming the film.Thus, the conventional methods have their limitations.

Carbon nanotubes have excellent electrical conductivity. A carbonnanotube film made of the carbon nanotubes, which is prepared by drawinga carbon nanotube array, has good electrical conductivity and a certaintransparence. However, the carbon nanotube film is composed of aplurality of carbon nanotubes joined by van der Waals attractive forcetherebetween. Thus, the strength of the carbon nanotube film drawn fromthe carbon nanotube array is relatively low.

What is needed, therefore, is to provide a carbon nanotube compositefilm with high strength to overcome the above limitations and a methodfor making the same.

BRIEF DESCRIPTION OF THE DRAWINGS

Many aspects of the embodiments can be better understood with referencesto the following drawings. The components in the drawings are notnecessarily drawn to scale, the emphasis instead being placed uponclearly illustrating the principles of the embodiments. Moreover, in thedrawings, like reference numerals designate corresponding partsthroughout the several views.

FIG. 1 is a flowchart of one embodiment of a method for making a carbonnanotube composite film.

FIG. 2 is a scanning electron microscope (SEM) image of an originalcarbon nanotube film.

FIG. 3 is a schematic view of one embodiment of a patterned carbonnanotube film with through holes substantially arranged in a row.

FIG. 4 is a schematic view of another embodiment of the patterned carbonnanotube film with through holes substantially arranged in a number ofrows.

FIG. 5 is a schematic view of one embodiment of a carbon nanotubecomposite film.

FIG. 6 is a schematic view of another embodiment of a carbon nanotubecomposite film.

FIG. 7 is a schematic view of one embodiment of a method for making acarbon nanotube composite film.

FIG. 8 is a schematic view of yet another embodiment of the patternedcarbon nanotube film including through holes used in the method of FIG.7.

FIG. 9 is an optical microscope image of the patterned carbon nanotubefilm including through holes of FIG. 8.

FIG. 10 is an optical microscope image of a treated patterned carbonnanotube film.

FIG. 11 is a schematic view of another embodiment of the carbon nanotubecomposite film.

FIG. 12 is an optical microscope image of another treated patternedcarbon nanotube film.

DETAILED DESCRIPTION

The disclosure is illustrated by way of example and not by way oflimitation in the figures of the accompanying drawings in which likereferences indicate similar elements. It should be noted that referencesto “an” or “one” embodiment in this disclosure are not necessarily tothe same embodiment, and such references mean at least one.

One embodiment of a carbon nanotube composite film 20 is provided. Thecarbon nanotube composite film 20 includes a treated patterned carbonnanotube film 22 and a film shaped polymer material 24 composited withthe treated patterned carbon nanotube film 22. The treated patternedcarbon nanotube film 22 includes a number of carbon nanotube linearunits 222 and a number of carbon nanotube groups 224. The carbonnanotube linear units 222 and the carbon nanotube groups 224 areconnected together and located in the same plane to cooperatively formthe film shape of the treated patterned carbon nanotube film 22. Thecarbon nanotube linear units 222 are spaced from each other. The carbonnanotube groups 224 join with the carbon nanotube linear 222 units byvan der Waals force. The carbon nanotube groups 224 located betweenadjacent carbon nanotube linear units 222 are separated from each other.The treated patterned carbon nanotube film 22 is located in the filmshaped polymer material 24.

The carbon nanotube linear units 222 substantially extend along a firstdirection, and are separated from each other along a second directioncrossed with the first direction. A shape of an intersection of eachcarbon nanotube linear unit 222 can be a semi-circle, circle, ellipse,oblate, or other shapes. In one embodiment, the carbon nanotube linearunits 222 are substantially parallel to each other, and distancesbetween adjacent carbon nanotube linear units 222 are substantiallyequal. The plurality of carbon nanotube linear units 222 aresubstantially coplanar. A diameter of each carbon nanotube linear unit222 is larger than or equal to 0.1 micrometers, and less than or equalto 100 micrometers. In one embodiment, the diameter of each carbonnanotube linear unit 222 is larger than or equal to 5 micrometers, andless than or equal to 50 micrometers. Distances between adjacent carbonnanotube linear units 222 are not limited and can be selected asdesired. In one embodiment, the distances between adjacent carbonnanotube linear units 222 are greater than 0.1 millimeters. Diameters ofthe carbon nanotube linear units 222 can be selected as desired. In oneembodiment, the diameters of the carbon nanotube linear units 222 aresubstantially equal. Each carbon nanotube linear unit 222 includes anumber of first carbon nanotubes substantially extending along the firstdirection. Adjacent first carbon nanotubes extending along the firstdirection are joined end to end by Van der Waals attractive force. Inone embodiment, an axis of each carbon nanotube linear unit 222 issubstantially parallel to the axis of first carbon nanotubes in eachcarbon nanotube linear unit.

The carbon nanotube groups 224 are separated from each other andcombined with adjacent carbon nanotube linear units 222 by van der Waalsforce along the second direction. The treated patterned carbon nanotubefilm 22 can be a free-standing structure. The “free-standing structure”means that the treated patterned carbon nanotube film 22 can sustain itssheet-shaped structure without any supporter. In one embodiment, thecarbon nanotube groups 224 arranged along the second direction areseparated from each other by the carbon nanotube linear units 222. Thecarbon nanotube groups 224 arranged along the second direction alsoconnect with the carbon nanotube linear units 222.

In one embodiment, the carbon nanotube groups 224 can be staggeredlylocated or disorderly arranged in the second direction. As such, thecarbon nanotube groups 224 in the second direction form non-straightconductive paths in the treated patterned carbon nanotube film 22. Inone embodiment, the carbon nanotube groups 224 are arranged into columnsin the second direction, thus the carbon nanotube groups 224 formconsecutive and straight conductive paths along the second direction inthe treated patterned carbon nanotube film 22. In one embodiment, thecarbon nanotube groups 224 in the treated patterned carbon nanotube film22 are arranged in an array. A length of each carbon nanotube group 224in the second direction is substantially equal to the distance betweenits adjacent carbon nanotube linear units 222, to connect the two carbonnanotube linear units 222 at the two sides of the carbon nanotube group224. The length of each carbon nanotube group 224 on the seconddirection is greater than 0.1 millimeters. The carbon nanotube groups224 are also spaced from each other along the first direction. Spacesbetween adjacent carbon nanotube groups 224 in the first direction aregreater than or equal to 1 millimeter. The first direction can besubstantially perpendicular to the second direction.

The carbon nanotube group 224 includes a number of second carbonnanotubes joined together by van der Waals force. Axes of the secondcarbon nanotubes can be substantially parallel to the first direction orthe carbon nanotube linear units 222. The axes of the second carbonnanotubes can also be crossed with the first direction or the carbonnanotube linear units 222. The second carbon nanotubes in each carbonnanotube group 224 can be crossed with each other to form a networkstructure.

The treated patterned carbon nanotube film 22 includes a number ofcarbon nanotubes. The carbon nanotubes form the carbon nanotube linearunits 222 and carbon nanotube groups 224. In one embodiment, the treatedpatterned carbon nanotube film 22 consists of the carbon nanotubes. Thetreated patterned carbon nanotube film 22 defines a number of apertures26. Specifically, the apertures 26 are mainly defined by the separatecarbon nanotube linear units 222 and the spaced carbon nanotube groups224. The arrangement of the apertures 26 is similar to the arrangementof the carbon nanotube groups 224. In the treated patterned carbonnanotube film 22, if the carbon nanotube linear units 222 and the carbonnanotube groups 224 are orderly arranged, the apertures 26 are alsoorderly arranged. In one embodiment, the carbon nanotube linear units222 and the carbon nanotube groups 224 are substantially arranged as anarray, the apertures 26 are also arranged as an array. A ratio of anarea sum of the carbon nanotube linear units 222 and the carbon nanotubegroups 224 to an area of the apertures is less than or equal to 1:19. Inother words, in treated patterned the carbon nanotube film 22, a ratioof the area having the carbon nanotubes to the area of the apertures 26is less than or equal to 1:19. In one embodiment, in the treatedpatterned carbon nanotube film 22, the ratio of the total sum area ofthe carbon nanotube linear units 222 and the carbon nanotube groups 224to the area of the apertures 26 is less than or equal to 1:49.Therefore, a transparency of the treated patterned carbon nanotube film22 is greater than or equal to 95%. In one embodiment, the transparencyof the treated patterned carbon nanotube film 22 is greater than orequal to 98%.

The treated patterned carbon nanotube film 22 is an anisotropicconductive film. The carbon nanotube linear units 222 form firstconductive paths along the first direction in the treated patternedcarbon nanotube film 22, as the carbon nanotube linear units 222 extendalong the first direction. The carbon nanotube groups 224 form secondconductive paths along the second direction in the treated patternedcarbon nanotube film 22. Therefore, a resistance of the treatedpatterned carbon nanotube film 22 along the first direction is differentfrom a resistance of the treated patterned carbon nanotube film 22 alongthe second direction. The resistance of the treated patterned carbonnanotube film 22 along the second direction is over 10 times greaterthan the resistance of the treated patterned carbon nanotube film 22along the first direction. In one embodiment, the resistance of thetreated patterned carbon nanotube film 22 along the second direction isover 20 times greater than the resistance of the treated patternedcarbon nanotube film 22 along the first direction. In one embodiment,the resistance of the treated patterned carbon nanotube film 22 alongthe second direction is about 50 times greater than the resistance ofthe treated patterned carbon nanotube film 22 along the first direction.In the treated patterned carbon nanotube film 22, the carbon nanotubelinear units 222 are joined by the carbon nanotube groups 224 on thesecond direction, which makes the treated patterned carbon nanotube film22 strong and stable.

It is noted that there can be a few carbon nanotubes randomlysurrounding the carbon nanotube linear units 222 and the carbon nanotubegroups 224 in the treated patterned carbon nanotube film 22. However,these few carbon nanotubes have a small and negligible effect on theproperties of the treated patterned carbon nanotube film 22.

The treated patterned carbon nanotube film 22 is composited in thepolymer material 24. The polymer material 24 has a continuous filmshape. The treated patterned carbon nanotube film 22 is embedded in thefilm of the polymer material 24. The polymer material 24 coats theentire outer surfaces of the carbon nanotube linear units 222 and thecarbon nanotube groups 224. The polymer material 24 also fills theapertures 26 and the inner space of the carbon nanotube linear units 222and the carbon nanotube groups 224 to combine the carbon nanotubes.

The polymer material 24 can be a thermosetting polymer or athermoplastic polymer, such as epoxy resin, polyolefin resin, acrylicresin, polyamide, polyurethane (PU), polycarbonate (PC), polyacetalresin (POM), polyethylene terephthalate (PET), polymethyl methacrylate(PMMA), silicone resin, and any combination thereof. The polymermaterial 24 can be a transparent material. The transparency of thecarbon nanotube composite film 20 depends on the transparencies of thepolymer material 24 and the treated patterned carbon nanotube film 22.The treated patterned carbon nanotube film 22 can have a transparencygreater than or equal to 95%. Thus, by using the transparent polymermaterial 24, the carbon nanotube composite film 20 can have atransparency greater than or equal to 90%.

The carbon nanotube composite film 20 can include a plurality of treatedpatterned carbon nanotube films 22 stacked and/or coplanar arranged inthe polymer material 24.

Referring to FIG. 1, one embodiment of a method for making the carbonnanotube composite film 20 includes the following steps:

S10, providing an original carbon nanotube film 120;

S20, forming a patterned carbon nanotube film 120′ by patterning theoriginal carbon nanotube film 120 to define at least one row of throughholes arranged in the original carbon nanotube film 120 along the firstdirection, each row of the through holes including at least two spacedthough holes 122;

S30, treating the patterned carbon nanotube film 120′ with a solventsuch that the patterned carbon nanotube film 120′ is formed into atreated patterned carbon nanotube film 22; and

S40, compositing the treated patterned carbon nanotube film 22 with apolymer material 24 to achieve the carbon nanotube composite film 20.

In step S10, the original carbon nanotube film 120 can be shown in FIG.2. The original carbon nanotube film 120 includes a number of carbonnanotubes joined end to end by van der Waals attractive force andsubstantially extending along a first direction. The original carbonnanotube film 120 can be obtained by drawing from a carbon nanotubearray 110 substantially along the first direction. Specifically, theoriginal carbon nanotube film 120 can be made by the steps of: providingthe carbon nanotube array 110 including a number of substantiallyparallel carbon nanotubes; and selecting carbon nanotubes from thecarbon nanotube array 110 and pulling the selected carbon nanotubessubstantially along the first direction, thereby forming the originalcarbon nanotube film 120.

In one embodiment, the carbon nanotube array 110 is formed on asubstrate 112, and the carbon nanotubes in the carbon nanotube array 110are substantially perpendicular to the substrate. During the pullingprocess, as the initial carbon nanotubes are drawn out and separatedfrom the substrate 112, other carbon nanotubes are also drawn out end toend due to van der Waals force between ends of adjacent carbonnanotubes. This process of pulling produces the original carbon nanotubefilm 120 with a certain width. The extending direction of the carbonnanotubes in the original carbon nanotube film 120 is substantiallyparallel to the pulling direction of the original carbon nanotube film120. Therefore, the original carbon nanotube film 120 consists of carbonnanotubes, and the carbon nanotubes are combined by van der Waals force.The original carbon nanotube film 120 is a free-standing structure. Thecarbon nanotubes in the original carbon nanotube film 120 define anumber of micropores, and effective diameters of the micropores are lessthan 100 nanometers.

The step S20 is mainly used to form spaced through holes 122 arrangedalong the first direction in the original carbon nanotube film 120. Theoriginal carbon nanotube film 120 can be patterned by using laser beamsor electron beams irradiate the original carbon nanotube film 120.

In one embodiment, the original carbon nanotube film 120 is patterned bylaser beams, and the step S20 includes the following sub-steps. A laseris provided. An irradiating path of a laser beam emitted from the lasercan be controlled by a computer. A shape data of the original carbonnanotube film 120 having the though holes 122 are inputted into thecomputer, which controls the irradiating path of the laser beam. Thelaser irradiates the original carbon nanotube film 120 to form thethrough holes 122. A power density of the laser beam ranges from about10000 watts per square meter to about 100000 watts per square meter anda moving speed of the laser beam ranges from about 800 millimeters persecond (mm/s) to about 1500 mm/s. In one embodiment, the power densityis in a range from about 70000 watts per square meter to about 80000watts per square meter, and the moving speed is in a range from about1000 mm/s to about 1200 mm/s.

In step S20, a shape of each through hole 122 can be a circle, ellipse,triangle, polygon, quadrangle, or other shapes. The quadrangle shape canhave at least one pair of parallel sides, such as a parallelogram,trapezia, rectangle, square, or rhombus. In one embodiment, the shape ofeach through hole 122 is rectangular. In another embodiment, the shapeof the through hole 122 is a straight line, which can be considered as arectangle with a narrow width. A size of the through hole 122 andmicropore represents the maximum distance between one point to anotherpoint both on the edge of the through hole 122 and micropore. Aneffective size of the through hole 122 is larger than the effective sizeof the micropore in the original carbon nanotube film 120. In oneembodiment, the effective size of the through hole 122 is larger than orequal to 0.1 millimeters. In one embodiment, a shape of the through hole122 is a rectangle having sides larger than 0.1 millimeters. A spacebetween adjacent through holes 122 is larger than the effective size ofthe micropore in the original carbon nanotube film 120. In oneembodiment, the space between adjacent through holes 122 is larger thanor equal to 0.1 millimeters. The shape and effective size of the throughhole 122 and the space between adjacent through holes 122 can beselected as desired. In one embodiment, the shape of the through hole122 is square having edges larger than or equal to 0.1 millimeters, andthe distance between the adjacent through holes 122 is larger than orequal to 0.1 millimeters.

In step S20, the patterned carbon nanotube film 120′ can be divided intoa number of connecting parts 124 and at least two extending parts 126 bythe through holes 122. The connecting parts 124 are located betweenadjacent through holes 122 in each row. The connecting parts 124 areseparated from each other along the first direction by the through holes122. The at least two extending parts 126 substantially extend along thefirst direction. The at least two extending parts 126 are connected witheach other on the second direction by the connecting parts 124.Therefore, the at least two extending parts 126 and the connecting parts124 are an integrated structure. Specifically, structures of thepatterned carbon nanotube films 120′ can be described as follow:

(1) Referring to FIG. 3, a number of through holes 122 are separatelyformed in a patterned carbon nanotube film 120′. The through holes 122are arranged into only one row along a first direction X. The firstdirection X is substantially parallel to the extending direction of thecarbon nanotubes in the patterned carbon nanotube film 120′. Thepatterned carbon nanotube film 120′ can be divided into a number ofconnecting parts 124 and two extending parts 126 by the through holes122. The connecting parts 124 are parts of the patterned carbon nanotubefilm 120′ between adjacent through holes 122 in the same row. The twoextending parts 126 are parts of the patterned carbon nanotube film 120′except the connecting parts 124.

The connecting parts 124 are separated from each other by the thoughholes 122. The connecting parts 124 and the though holes 122 in the samerow are alternately arranged. The two extending parts 126 are located onopposite sides of the connecting parts 124. The extending parts 126 aredivided by the connecting parts 124 along a second direction Y crossedwith the first direction X. In one embodiment, the second direction Y issubstantially perpendicular to the first direction X. Each extendingpart 126 extends along the first direction X.

(2) Referring to FIG. 4, a number of through holes 122 are arranged intoa number of rows in the patterned carbon nanotube film 120′. The throughholes 122 in the same row are spaced from each other along the firstdirection X. The through holes 122 are staggered with each other alongthe second direction Y. That is, the through holes 122 in the seconddirection Y are not arranged in a straight line. It can be understoodthat the through holes 122 in the second direction Y can also bearranged in columns, and the through holes 122 in the same column arespaced from each other. The through holes 122 can be arranged as anarray.

The patterned carbon nanotube film 120′ is divided into a number ofconnecting parts 124 and a number of extending parts 126 by the throughholes 122. Every adjacent connecting parts 124 in the same row areseparated by the through hole 122. A length of each connecting part 124is equal to a space between adjacent through holes 122 in the same rowalong the first direction X. Each extending part 126 is a connectivestructure along the first direction X. Each extending part 126 issandwiched between adjacent connecting parts 124 in the second directionY. A width of each extending part 126 in the second direction Y is equalto a space between adjacent through holes 122 in the second direction Y.The extending parts 126 connect with adjacent connecting parts 124arranged along the second direction Y. In one embodiment, an effectivelength of each through hole 122 in the first direction X is larger thana space between adjacent through holes 122 along the second direction Y.The extending parts 126 and the connecting parts 124 are belonged to theintegrated structure of the patterned carbon nanotube film 120′.

The shapes of the through holes 122 or the space between adjacentthrough holes arranged in the same row or in the same column can bedifferent. In the patterned carbon nanotube film 120′, the arrangementof the connecting parts 124 is similar to the arrangement of the throughholes 122. There are a few carbon nanotubes protruding around edges ofeach through holes 122, which is a result of the manufacturing processof the carbon nanotube film 22.

In step S30, the patterned carbon nanotube film 120′ is suspended. Thestep S30 can include dropping or spraying the solvent on the suspendedpatterned carbon nanotube film 120′, and further shrinking the patternedcarbon nanotube film 120′ into the treated patterned carbon nanotubefilm 22. Because the carbon nanotubes in each extending part of theoriginal carbon nanotube film 120 are substantially joined end-to-endand substantially oriented along the first direction, and each extendingpart 126 of the original carbon nanotube film 120 is a consecutivestructure on the first direction, the extending parts 126 in theoriginal carbon nanotube film 120 are shrunk into the carbon nanotubelinear units 222 of the treated patterned carbon nanotube film 22 underinterfacial tension of the solvent as it dissipates (e.g., volatilizes).During the treating process with the solvent, each extending part 126 ofthe patterned carbon nanotube film 120′ is substantially shrunk towardits center in the second direction and formed into the carbon nanotubelinear unit 222, a space between adjacent extending parts 126 will beincreased. Therefore, the carbon nanotube linear units 222 are spacedfrom each other in the treated patterned carbon nanotube film 22. Aspace between adjacent carbon nanotube linear units 222 in the treatedpatterned carbon nanotube film 22 is larger than the effective diameterof the through holes 122 connected with the extending part 126 or largerthan the effective diameter of the through holes 122 defined in thepatterned carbon nanotube film 120′ in the second direction (e.g.,larger than 0.1 millimeters). Simultaneously, each connecting part 124will be pulled along the second direction due to the shrinking of theadjacent extending parts 126. The orientation of the carbon nanotubes inthe connecting part may be varied due to the pulling. The connectingpart 124 is formed into the carbon nanotube group 224 in the treatedpatterned carbon nanotube film 22. Therefore, the treated patternedcarbon nanotube film 22 is formed.

An interfacial tension is generated between the patterned carbonnanotube film 120′ and the solvent, and the interfacial tension variesdepending on the volatility of the solvent. Pulling tensions applied tothe connecting parts 124 are produced by the shrinking of the extendingparts 126. The pulling tensions vary depending on the interfacialtension. Different solvent may have different pulling forces to thecarbon nanotubes in the patterned carbon nanotube film 120′. The pullingtensions can affect the arrangement of the carbon nanotubes in theconnecting parts 124, and further affect the structures of the carbonnanotube groups 224 in the treated patterned carbon nanotube film 22.Different solvent may result different arrangement of the carbonnanotubes in the carbon nanotube groups 224.

If the solvent is an organic solvent with a high volatility, such asalcohol, methanol, acetone, dichloroethane, or chloroform, theinterfacial tension generated between the patterned carbon nanotube film120′ and the solvent is strong. During the process of shrinking theextending parts 126, pulling forces are produced. The pulling forcesapplied to the connecting parts 124 adjacent to the extending parts 126are strong. The carbon nanotubes oriented along the first direction inthe connecting parts 124 will be formed into the second carbon nanotubesextending along a direction crossing with the first direction.Simultaneously, under the interfacial tension, the carbon nanotubes ineach connecting part 124 will be shrunk and each connecting part 124will be formed into the carbon nanotube group 224 with a net structure.In one embodiment, a first angle defined by the second carbon nanotubesand the first direction is greater than or equal to 45 degrees, and lessthan or equal to 90 degrees.

If the solvent is water, or a mixture of water and the organic solvent,the interfacial force between the patterned carbon nanotube film 120′and the solvent is relatively weak. The pulling forces generated by theshrinking of the extending parts 126 are weak, thus the pulling forcesare weakly applied to the connecting parts 124. The arrangements of thecarbon nanotubes in the connecting parts 124 will be a little changed bythe weak pulling forces. A second angle is defined by the second carbonnanotubes in the carbon nanotube groups 224 with the first direction.The second angle is less than or equal to 30 degrees. In one embodiment,the second angle is less than or equal to 15 degrees. In one embodiment,the first solvent is water, and during the process of forming the carbonnanotube linear units 222, the arrangements of carbon nanotubes in theconnecting parts 124 are substantially not changed. Therefore, thesecond carbon nanotubes in the carbon nanotube groups are substantiallyparallel to the carbon nanotube linear units 222 and the firstdirection.

In the step S20, if the through holes 122 are arranged in rows, thecarbon nanotube linear units 222 made from the extending parts 126 ofthe original carbon nanotube film 120, will be substantially parallel toeach other. If the through holes 122 are arranged in rows and columns,the extending parts 126 will be formed into carbon nanotube linear units222 substantially extending along the first direction, and the carbonnanotube linear units 222 are separately arranged on the seconddirection. At the same time, the connecting parts 124 will be formedinto the carbon nanotube groups 224, and the carbon nanotube groups 224will connect with the carbon nanotube linear units 222 on the seconddirection and be spaced in the first direction. The carbon nanotubelinear units 222, which are substantially parallel and separate on thesecond direction, form the first conductive paths substantiallyextending along the first direction. The carbon nanotube groups 224 areconnected with the carbon nanotube linear units 222 in the seconddirections and spaced in the first direction, which form the secondconductive paths extending along the second direction.

Therefore, the diameters of the carbon nanotube linear units 222 dependson the spaces between adjacent through holes 122 in the second directionand the shapes of the through holes 122. Spaces between adjacent carbonnanotube linear units 222 can be controlled by the spaces betweenadjacent through holes 122 in the second direction and the widths ofthrough holes 122 in the second direction. In one embodiment, the shapeof the through holes 122 is rectangular, the widths of the through holesin the second direction are equal, and the spaces between adjacentthough holes 122 in the same rows are equal. Therefore, the shapes andthe diameters of the carbon nanotube linear units 222 are respectivelyequal. Further, if the lengths of the through holes 122 in the firstdirections are equal, the carbon nanotube groups 224 will besubstantially arranged in the second direction and the shapes of thecarbon nanotube groups 224 will be substantially the same. Inconclusion, both the spaces between adjacent carbon nanotube linearunits 222 and the diameter of the carbon nanotube linear units 222 canbe effectively and easily adjusted according to the method for makingthe treated patterned carbon nanotube film 22 provided by the presentdisclosure.

Under the same condition, a resistance of the treated patterned carbonnanotube film 22 along the first direction is not affected by the numberof the through holes 122 arranged along the first direction. The morethrough holes 122 that are arranged along the first direction, thehigher a resistance of the treated patterned carbon nanotube film 22along the second direction. The less through holes 122 that are arrangedalong the first direction, the lower the resistance of the treatedpatterned carbon nanotube film 22 along the second direction. Under thesame condition, the resistance of the treated patterned carbon nanotubefilm 22 along the second direction is not affected by the number of thethrough holes 122 in the patterned carbon nanotube film 120′ along thesecond direction. The more through holes 122 that are arranged along thesecond direction, the higher a resistance of the treated patternedcarbon nanotube film 22 along the first direction. The less throughholes 122 that are arranged along the second direction, the lower theresistance of the treated patterned carbon nanotube film 22 along thefirst direction. Therefore, the resistance of the treated patternedcarbon nanotube film 22, especially the electrical anisotropy of thetreated patterned carbon nanotube film 22, can be changed by the numberof the through holes 122 in the patterned carbon nanotube film 120′.That is, the step S20 can affect the resistance of the treated patternedcarbon nanotube film 22.

It is noted that, the electrical conductivity of the treated patternedcarbon nanotube film 22 can be affected by parameters of the throughholes 122. If the through holes 122 are uniformly distributed in thepatterned carbon nanotube film 120′ and each through hole 122 isrectangular, the length of each through hole 122 in the first directionis marked as parameter A, the width of each through hole 122 in thesecond direction is marked as parameter B, the space between adjacentthrough holes 122 in the first direction is marked as parameter C, andthe space between adjacent through holes 122 in the second direction ismarked as parameter D. In one embodiment, the parameter A is smallerthan the parameter D. If compared with the parameter A, the parameter Bis relatively small, the through holes 122 can be considered as straightlines. The affect of the parameters of the through holes 122 on theresistance and electrical anisotropy of the treated patterned carbonnanotube film 22 can be detailed below:

(1) If the parameters A and B are constant, the ratio of the resistanceof the treated patterned carbon nanotube film 22 along the seconddirection to the resistance of the treated patterned carbon nanotubefilm 22 along the first direction is increased as the ratio of theparameter A to parameter B (A/B) increases. The electrical anisotropy ofthe treated patterned carbon nanotube film 22 is proportional to theratio of the parameter A to parameter B.

(2) If the parameters A and C are constant, the resistance of thetreated patterned carbon nanotube film 22 at the first direction isincreased as the ratio of the parameter B to parameter D (B/D)increases.

(3) If the parameters B and D are constant, the resistance of thetreated patterned carbon nanotube film 22 along the second direction isincreased as the ratio of the parameter A to parameter C (A/C)increases. In addition, the electrical anisotropy of the treatedpatterned carbon nanotube film 22 can be improved by decreasing theratio of the parameter A to the parameter C.

During patterning the original carbon nanotube film 120 and treating thepatterned carbon nanotube film 120′, the original carbon nanotube film120 and the patterned carbon nanotube film 120′ can be fixed at twoopposite ends. When the original carbon nanotube film 120 is drawn fromthe carbon nanotube array 110, the end away from the carbon nanotubearray 110 of the original carbon nanotube film 120 can be fixed to afixing element 128, e.g., a collecting unit.

The method for making the carbon nanotube composite film 20 furtherincludes a step of collecting the carbon nanotube composite film 20.Specifically, one end of the original carbon nanotube film 120 drawnfrom the carbon nanotube array 110 is fixed on the collecting unit. Thecollecting unit is rolled, the original carbon nanotube film 120 can becontinuously patterned and treated with the polymer solution in order,and then the carbon nanotube composite film 20 is continuously formedand rolled up on the collecting unit. Thus, the carbon nanotubecomposite film 20 can be continuously formed as the rolling of thecollecting unit. The carbon nanotube composite film 20 can be producedautomatically.

In the step S40, the compositing step can further include: forming aliquid state coating layer containing at least one of the polymermaterial 24 and monomer of the polymer material 24 on a surface of asubstrate; laying the treated patterned carbon nanotube film 22 on theliquid state coating layer; and solidifying the liquid state coatinglayer.

The molten stated polymer material 24, a molten stated monomer of thepolymer material 24, a liquid solution of the polymer material 24, or aliquid solution of the monomer of the polymer material 24 can be coatedon the surface of the substrate, to form the liquid state coating layerof the polymer material 24 of a liquid state coating layer of themonomer of the polymer material 24. The liquid solution of the polymermaterial 24 is obtained by dissolving the polymer material 24 in asolvent. The liquid solution of the monomer of the polymer material 24is obtained by dissolving the monomer of the polymer material 24 in thesolvent. The solvent can be water, ethanol, methanol, acetone,dichloroethane, chloroform, or combinations thereof. The polymermaterial 24 can be the thermosetting polymer or thermoplastic polymerthat is capable of being dissolved in the solvent.

The treated patterned carbon nanotube film 22 can be laid on the liquidstate coating layer and embedded into the liquid state coating layer dueto the gravity. Then, the liquid state coating layer having the treatedpatterned carbon nanotube film 22 therein is solidified. To solidify theliquid state coating layer, the molten stated polymer material 24 can becured, the solvent of the liquid solution can be removed, and themonomer of the polymer material 24 can be polymerized to in-situ formthe polymer material 24.

In another embodiment, the treated patterned carbon nanotube film 22 canbe sandwiched between two solid films of polymer material 24 and thenthe solid films are heated to be melted. During the heating, a pressurecan be applied to the heated films of polymer material 24 from twoopposite sides, to press the melted polymer material 24 into themicropores of the treated patterned carbon nanotube film 22. After themelted polymer material 24 is infiltrated into the treated patternedcarbon nanotube film 22, the polymer material 24 is solidified.

The polymer material 24 can be infiltrated into the micropores betweenthe carbon nanotubes in the carbon nanotube linear units 222 and thecarbon nanotube groups 224 of the treated patterned carbon nanotube film22, to composite with the treated patterned carbon nanotube film 22. Theapertures 26 of the treated patterned carbon nanotube film 22 can alsobe filed with the polymer material 24.

The carbon nanotube composite films 20 and the methods for making thecarbon nanotube composite films 20 can be further described in thefollowing embodiments.

Referring to FIG. 5, one embodiment of carbon nanotube composite film 20is provided. The carbon nanotube composite film 20 includes a treatedpatterned carbon nanotube film 22 and a transparent polymer material 24having the treated patterned carbon nanotube film 22 located therein.The treated patterned carbon nanotube film 22 is a free-standingstructure, and includes a number of carbon nanotube linear units 222 anda number of carbon nanotube groups 224. The carbon nanotube groups 224are connected between the adjacent two carbon nanotube linear units 222by van der Waals force. The carbon nanotube linear units 222 areinserted among the carbon nanotube groups 224.

The carbon nanotube linear units 222 are substantially parallel to eachother and separate from each other along the second direction Y. Thecarbon nanotube linear units 222 extend along the first direction Xwhich is substantially perpendicular to the second direction Y, to formthe first conductive paths. The first direction X can be substantiallyperpendicular to the second direction Y. Each carbon nanotube linearunit 222 consists of carbon nanotubes joined end-to-end by van der Waalsforce and substantially extend along the first direction X. The diameterof the carbon nanotube linear unit 222 is about 10 micrometers. Thespace between adjacent two carbon nanotube linear units 222 is widerthan 1 millimeter.

The plurality of carbon nanotube groups 224 are arranged in an array.Specifically, the carbon nanotube groups 224 are spaced from each otheralong the first direction X. The carbon nanotube groups 224 are orderlyarranged in columns along the second direction Y and connected with thecarbon nanotube linear units 222 to form the second conductive paths.Each carbon nanotube group 224 includes the carbon nanotubes intersectedwith each other to form a network structure. The extending directions ofthe carbon nanotubes in the carbon nanotube groups 224 are not parallelto the first direction X. Angles defined between the extendingdirections of the carbon nanotubes in the carbon nanotube groups 224 andthe first direction X are greater than or equal to 60 degrees, and lessthan or equal to 90 degrees.

It is noted that there can be a few carbon nanotubes randomlysurrounding the carbon nanotube linear units 222 and the carbon nanotubegroups 224 in the carbon nanotube film 22. However, these few carbonnanotubes have a small and negligible effect on the properties of thetreated patterned carbon nanotube film 22.

The polymer material 24 has a continuous shape (e.g., a film shape), andhas the treated patterned carbon nanotube film 22 located therein.

The carbon nanotube composite film 20 has different structures in thefirst direction X and the second direction Y. Therefore, the carbonnanotube composite film 20 has different properties in the first andsecond direction X, Y. The carbon nanotube composite film 20 is anelectrically anisotropic film. The resistance of the carbon nanotubecomposite film 20 in the second direction Y can be about 50 timesgreater than that in the first direction X. The polymer material 24 canbe a PET film with a high transparency. The carbon nanotube compositefilm 20 can have a relatively small thickness such as about 10 microns.Thus, the carbon nanotube composite film 20 can have a relatively hightransparency.

It can be understood that the carbon nanotube composite film 20 can alsohave a structure as shown in FIG. 6, in which the carbon nanotube groups224 are in a staggered arrangement in the second direction Y.Specifically, the carbon nanotube groups 224 are arranged in rows in thefirst direction X, and disorderly arranged in the second direction Y. Inanother embodiment, the carbon nanotube groups 224 are in a staggeredarrangement in the first direction X. That is, the carbon nanotubegroups 224 are arranged in columns in the second direction Y, anddisorderly arranged in the first direction X.

In some embodiments, the sizes of the carbon nanotube groups 224 do notneed to be the same. The sizes of the carbon nanotube linear units 222also do not need to be the same.

Referring to FIG. 7, one embodiment of the method for making the carbonnanotube composite film 20 is provided. The method includes thefollowing steps.

A carbon nanotube array 110 is provided. The carbon nanotube array 10 isgrown on a growing substrate 112. An original carbon nanotube film 120is drawn from the carbon nanotube array 110 using an adhesive tape 114.The original carbon nanotube film 120 includes a number of carbonnanotubes joined end to end by van der Waals force and substantiallyextending along the first direction X.

The adhesive tape 114 is removed. The end of the original carbonnanotube film 120 adhered to the adhesive tape 114, is fixed on a fixingelement 128. The fixing element 128 can be a bar. The original carbonnanotube film 120 between the fixing element 128 and the carbon nanotubearray 110 is suspended. The suspended original carbon nanotube film 120is patterned by a laser with a power density of about 70000 watts persquare millimeter, and a scanning speed of about 1100 millimeters perseconds. A number of rectangular through holes 122 are defined in theoriginal carbon nanotube film 120. The through holes 122 are uniformlyarranged in rows and columns. Referring to FIGS. 8 and 9, the patternedcarbon nanotube film 120′ is divided into a number of connecting parts124 and a number of extending parts 126 by the through holes 122. Theconnecting parts 124 are arranged in an array, which is similar to thearrangement of the through holes 122. The spaces between adjacentthrough holes 122 both in the first direction X and the second directionY are about 1 millimeter. The length of the through hole 122 in thefirst direction X is about 3 millimeters. The width of the through hole122 in the second direction Y is about 1 millimeter. That is, theparameters A, B, C and D of each through hole 122 are respectively about3 millimeters, 1 millimeter, 1 millimeter, and 1 millimeter. Thus, thelengths of the connecting part 124 in the first direction X and thesecond direction Y are about 1 millimeter. The width of the extendingpart 126 in the second direction Y is equal to the parameter D of thethrough hole 122.

A drop bottle 130 is placed above the patterned carbon nanotube film120′. Alcohol is dropped onto the patterned carbon nanotube film 120′from the drop bottle 130. Under interfacial tension produced between theextending part 126 and the alcohol, each extending part 126 is shrunktoward its center to form the carbon nanotube linear unit 222. The sizeof the through holes 122 is increased in the width direction, and thus,the through holes 122 are formed into the apertures 26. Simultaneously,a pulling force is produced in the process of the shrinking of theextending part 126. Under the pulling force and the interfacial tensionproduced between the connecting part 124 and the alcohol, extendingdirections of most of the carbon nanotubes in the connecting part 124are shifted into directions intersecting with the first direction, andthe carbon nanotube group 224 is formed. The carbon nanotube groups 224are connected with the carbon nanotube linear units 222 in the seconddirection, and separated from each other in the first direction. Thus,referring to FIG. 10, the treated patterned carbon nanotube film 22 isformed.

There are some carbon nanotubes protruding from the edges of the throughholes 122 resulting from limitations of the laser. After the process oftreatment with the solution, there can still be a few carbon nanotubesextending from the peripheries of the carbon nanotube linear units 222and the carbon nanotube groups 224.

If the through holes are arranged in the staggered, disorderedarrangement in the second direction Y as shown in FIG. 4, the carbonnanotube composite film 20 shown in FIG. 6 obtained by theabove-mentioned method, includes the staggered carbon nanotube groups224.

A molten stated PET is coated on a surface of a substrate to form acoating layer. The treated patterned carbon nanotube film 22 is laid onthe coating layer and embedded into the coating layer. Then, the coatinglayer is solidified, to form the carbon nanotube composite film 20.

Referring to FIG. 11, another embodiment of a carbon nanotube compositefilm 30 is provided. The carbon nanotube composite film 30 includes acarbon nanotube film 32 and a polymer material 24 composited with thecarbon nanotube film 32. The carbon nanotube film 32 is a free-standingstructure and includes a number of the carbon nanotube linear units 322and a number of carbon nanotube groups 324 arranged in an array. Thecarbon nanotube group 324 is connected between two adjacent carbonnanotube linear units 322 by van der Waals attractive force. Thestructure of the carbon nanotube composite film 30 is similar to that ofthe carbon nanotube composite film 20, except that the carbon nanotubegroups 324 includes a number of carbon nanotubes substantially extendingalong the first direction X. The carbon nanotube linear units 322 extendalong the first direction X. That is, the carbon nanotubes in the carbonnanotube composite film 30 are substantially oriented along the samedirection, which is the same as the extending direction of the carbonnanotube linear units 322.

A method for making the carbon nanotube composite film 30 is similar tothe method for making the carbon nanotube composite film 20, except thatin the step S30, water is used as the solvent to treat the patternedcarbon nanotube film 120′ having a number of through holes 122 formed bylaser.

The apertures in the treated patterned carbon nanotube film are filedwith the polymer material, and thus the carbon nanotube composite filmof the present disclosure has improved mechanical properties, such as agood strength. The carbon nanotube composite film has a film shape andis a free-standing structure, thus has a variety of use, such as in atouch panel and a heater.

It is to be understood that the above-described embodiment is intendedto illustrate rather than limit the disclosure. Variations may be madeto the embodiment without departing from the spirit of the disclosure asclaimed. The above-described embodiments are intended to illustrate thescope of the disclosure and not restricted to the scope of thedisclosure.

It is also to be understood that the above description and the claimsdrawn to a method may include some indication in reference to certainsteps. However, the indication used is only to be viewed foridentification purposes and not as a suggestion as to an order for thesteps.

What is claimed is:
 1. A carbon nanotube composite film, comprising: atreated patterned carbon nanotube film comprising: a plurality of carbonnanotube linear units spaced from each other; and a plurality of carbonnanotube groups spaced from each other and combined with the pluralityof carbon nanotube linear units; and a polymer film having the treatedpatterned carbon nanotube film located therein.
 2. The carbon nanotubecomposite film of claim 1, wherein the plurality of carbon nanotubelinear units are substantially parallel to each other and are alignedalong a first direction to form a plurality of first conductive paths.3. The carbon nanotube composite film of claim 2, wherein the pluralityof carbon nanotube groups are spaced from each other in the firstdirection and are combined with the plurality of carbon nanotube linearunits in a second direction, that intersects the first direction, toform a plurality of second conductive paths, the plurality of firstconductive paths intersect with the plurality of second conductivepaths.
 4. The carbon nanotube composite film of claim 3, wherein theplurality of carbon nanotube groups are arranged in a staggered mannerin the second direction.
 5. The carbon nanotube composite film of claim3, wherein the plurality of carbon nanotube groups are arranged incolumns in the second direction.
 6. The carbon nanotube composite filmof claim 1, wherein each carbon nanotube linear unit comprises aplurality of carbon nanotubes joined end-to-end by van der Waals forceand substantially oriented along an axis direction of the each carbonnanotube linear unit.
 7. The carbon nanotube composite film of claim 1,wherein a diameter of each carbon nanotube linear unit is greater thanor equal to 0.1 micrometers, and less than or equal to 100 micrometers.8. The carbon nanotube composite film of claim 1, wherein each carbonnanotube group comprises a plurality of carbon nanotubes substantiallyextending along an axis direction of each carbon nanotube linear unit.9. The carbon nanotube composite film of claim 1, wherein each carbonnanotube group comprises a plurality of carbon nanotubes intersectedwith an axis direction of each carbon nanotube linear unit.
 10. Thecarbon nanotube composite film of claim 1, wherein a distance betweenadjacent carbon nanotube linear units is larger than 0.1 millimeters.11. The carbon nanotube composite film of claim 1, wherein a distancebetween adjacent carbon nanotube groups located between same twoadjacent carbon nanotube linear units is larger than 1 millimeter. 12.The carbon nanotube composite film of claim 1, wherein the plurality ofcarbon nanotube groups are combined with the plurality of carbonnanotube linear units by van der Waals attractive force.
 13. The carbonnanotube composite film of claim 1, wherein the plurality of carbonnanotube linear units and the plurality of carbon nanotube linear unitsdefine a plurality of micropores by carbon nanotubes, a polymer materialof the polymer film is infiltrated into the plurality of micropores. 14.A method for making carbon nanotube composite film, comprising:providing an original carbon nanotube film; forming a patterned carbonnanotube film by patterning the original carbon nanotube film to defineat least one row of through holes arranged in the original carbonnanotube film along a first direction, each row of the through holescomprises at least two though holes; treating the patterned carbonnanotube film with a solvent such that a treated patterned carbonnanotube film is formed; and compositing the treated patterned carbonnanotube film with a polymer material to achieve the carbon nanotubecomposite film.
 15. The method of claim 14, wherein the patterning theoriginal carbon nanotube film comprises using a laser beam or anelectron beam to irradiate the original carbon nanotube film.
 16. Themethod of claim 14, wherein a shape of each through hole is a circle,ellipse, triangle, polygon, or quadrangle.
 17. The method of claim 14wherein the treating the patterned carbon nanotube film furthercomprises: suspending the patterned carbon nanotube film to obtain asuspended patterned carbon nanotube film; applying the solvent on thesuspended patterned carbon nanotube film, and shrinking the patternedcarbon nanotube film into the treated patterned carbon nanotube film.18. The method of claim 14, wherein the solvent is selected from thegroup consisting of water, ethanol, methanol, acetone, dichloroethane,chloroform, and combinations thereof.
 19. The method of claim 14,wherein the compositing the treated patterned carbon nanotube filmcomprising: forming a liquid state coating layer containing at least oneof the polymer material and monomer of the polymer material on a surfaceof a substrate; laying the treated patterned carbon nanotube film on theliquid state coating layer; and solidifying the liquid state coatinglayer.
 20. The method of claim 14, wherein the compositing the treatedpatterned carbon nanotube film comprises: sandwiching the treatedpatterned carbon nanotube film between two solid films of the polymermaterial; heating to melt the polymer material of the two solid films;and solidifying the polymer material.